The increase of the eosinophil leukocytes can be taken as a sign of an allergic reaction it might be a helpful means for obtaining information on the etiology of diseases, therefore, examinations for eosinophil leukocytes in Cantharidin blisters was undertaken in normals and with various skin disorders. 1. In 30 healthy suhjects, blister eontained 56.47+42.5/mm3 of eosinophil leucocytes, and 80% of them never exceeded 66/mm3 of eosinophil leucocytes. 2. The highest eosinophil leukocytes among the various dermatoses was seen contact dermatitis (93.07+40.3/mm3) and drug eruption (92.17+21.1/mm3), atopic dermatitis (75.37+41.0/mm3), and chronic urticaria (72.28+24.2/mm3) were followed in order. 3. The eosinophil leukocytes were slightly increased in psoriasis vulgaris (69.14+29.9/mm3) and herpes zoster (63.25+20.4/mm3). 4. The eosinophil leucocytes were markedly increased in the skin disorders of allergic nature and slightly in non-allergic skin disorders.